Plastic containers with gas barrier coating and optionally hydrophilic inside coating

Abstract

The invention is directed to a process for producing a plastic container with a barrier coating comprising a) applying at least one coating layer of a first polyvinyl acetal on at least a part of the plastic container; b) applying at least one coating layer of polyvinyl alcohol on the first polyvinyl acetal layer; c) applying at least one top coating layer of a second polyvinyl acetal on the polyvinyl alcohol layer. The surface of the plastic container may be pre-treated before coating. In addition to the barrier coating, the surface energy of at least a part of the inside surface of the plastic container may be increased by applying at least one inner hydrophilic coating layer.

The invention claimed is: 
     
       1. A process for producing a plastic container with a barrier coating, said process comprising:
 a) applying at least one coating layer of a first polyvinyl acetal on at least a part of the plastic container; 
 b) applying at least one coating layer consisting of polyvinyl alcohol on the first polyvinyl acetal layer; and 
 c) applying at least one top coating layer of a second polyvinyl acetal on the polyvinyl alcohol layer. 
 
     
     
       2. The process according to  claim 1 , wherein, prior to a), the plastic container is subjected to a pre-treatment wherein the plastic container is pre-treated by chemical roughening, oxyfluorination, corona, electron beam or flame treatment. 
     
     
       3. The process according to  claim 2 , wherein the surface energy of the plastic container is increased by the pre-treatment by at least 10%. 
     
     
       4. The process according to  claim 1 , wherein the barrier coating is applied on at least a part of the outside of the plastic container. 
     
     
       5. The process according to  claim 1 , wherein the barrier coating is applied on at least a part of the inside of the plastic container. 
     
     
       6. The process according to  claim 1 , wherein the barrier coating is applied on at least a part of the inside and at least a part of the outside of the plastic container. 
     
     
       7. The process according to  claim 1 , further comprising d) increasing the surface energy of at least a part of the inside surface of the plastic container by applying at least one inner hydrophilic coating layer. 
     
     
       8. The process according to  claim 7 , wherein the inner hydrophilic coating layer comprises vegetable fats or oils, glycerine esters, polyvinyl alcohol and/or polyvinyl acetal. 
     
     
       9. The process according to  claim 1 , wherein, subsequent to a), b), and c), the plastic container is shaped in a blow-forming process. 
     
     
       10. The process according to  claim 1 , wherein the coating layer consisting of polyvinyl alcohol is applied as aqueous solution and dried at 10-90° C. 
     
     
       11. The process according to  claim 1 , wherein each of the first and second polyvinyl acetals are selected from polyvinyl butyral, polyvinyl acetyl-co-butyral and crosslinked polyvinyl butyral. 
     
     
       12. The process according to  claim 1 , wherein the plastic container is first coated on the outside by a), b) and c), and then shaped in a blow-forming process. 
     
     
       13. The process according to  claim 12 , further comprising d) increasing the surface energy of at least a part of the inside surface of the plastic container by applying at least one inner hydrophilic coating layer, wherein the plastic container is coated on the inside by d) after shaping in a blow-forming process. 
     
     
       14. The process according to  claim 12 , further comprising d) increasing the surface energy of at least a part of the inside surface of the plastic container by applying at least one inner hydrophilic coating layer, wherein the plastic container is coated on the inside by d) prior to shaping in a blow-forming process. 
     
     
       15. The process according to  claim 12 , wherein the shaping of a preform is performed by a stretch blowing. 
     
     
       16. The process according to  claim 7 , wherein, subsequent to a), b), c) and d), the plastic container is shaped in a blow-forming process. 
     
     
       17. The process according to  claim 12 , wherein the shaping of a preform is performed by injection stretch blow molding. 
     
     
       18. The process according to  claim 2 , wherein the surface energy of the plastic container is increased by the pre-treatment by at least 25%. 
     
     
       19. The process according to  claim 11 , wherein the acetalization degree of the polyvinyl acetals is between 70 and 90 mol %. 
     
     
       20. The process according to  claim 1 , the polyvinyl alcohol has a degree of saponification/hydrolization of at least 90%, and the coating layer of polyvinyl alcohol has a thickness of 0.01 to 5 μm.